Radio transmitter-receiver jamming system



Patented Jan. 16, 1951 RADIO TRANSMITTER-RECEIVER J AMMING SYSTEM Everard M. Williams, State lCollege, Pa., assignor to the United States of America as represented by the Secretary of War Application January 23, 1945, Serial No. 574,165

(Cl. Z50-13) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) Claims.

The invention described herein maybe manufactored and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

. This invention relates to a radio receivertransmitter device and more particularly to a receiver for determining the frequency of an intercepted signal, and a transmitter, both embodied in a single circuit.

One of the objects of the present invention is to provide a single magnetron containing circuit that serves as a receiver, in which form the magnetron is tuned accurately to the frequency of an intercepted signal, and as a transmitter which uses the same magnetron as a source of radiated power for the transmitting operation.

Further objects of the invention comprise a receiver-transmitter that uses a magnetron as a combined oscillator and power tube for the purposes that are described herein; and that provides a modulator circuit for the magnetron oscillator which serves as a source of quenching voltage for operation of the magnetron as a superregenerative detector.

One illustrative embodiment of the invention that is contemplated herein and a modification thereof, that accomplish the above and other objects that will appear hereinafter, are shown in the accompanying drawing, wherein:

Fig. 1 is a schematic circuit drawing of the device that is contemplated herein; and

Fig. 2 is a fragmentary schematic drawing of a modification in the circuit that is shown in Fig. 1.

When the device is to serve as a receiver, a

radio signal is received from an antenna I that is grounded through an inductance loop 2. The antenna loop 2 is coupled inductively through suitable tunable means, such as a lecher line 3, or the like, to a tunable oscillating circuit which includes in push-pull the two plates of a twoplate magnetron 4. A voltage dropping resistor 5, in the plate supply circuit of the magnetron 4, drops supply voltage from a battery that has its positive post connected to the resistor 5 at its end that is remote from the end that vis attached to the movable bar of the lecher line 3 to a predetermined plate voltage value that is suitable for operation of the magnetron as a part of a superregenerative detector. The resistor 5 is shunted by a switch I8. The negative battery terminal of the supply voltage is grounded, as shown.

Heating current for the cathode of the magnetron 4 is supplied preferably by induction through suitable means, such as through a radio frequency transformer 6, or the like, that is coupled inductively with a primary winding from radio frequency oscillator 'I that oscillates at a low radio frequency.

The plate cathode circuit of a modulator tube 8 is inserted by a mid-tap on the secondary of the transformer 6. The cathode of the modulator 8 is grounded. The control grid of the tube 8 is connected through a two-way switch 9 to an oscillator I0 when the device is to be used as a receiver. The switch 9 is ganged to the switch I8. The oscillator IU oscillates at a supersonic frequency. The supersonic frequency from the oscillator Il] is applied by the modulator tube 8 between the cathode of the magnetron 3 and ground. When the switch 9 is in its receiving position the supersonic frequency from the oscillator IO supplies the quench voltage for the operation of the magnetron 4 as a superregenerative detector. When the switch 9 is in its transmit position it connects the modulator tube 8 with a noise source I'I.

The detected signal across the resistor 5 is applied through blocking condensers II and I6 to a video amplifier I2, thence t0 a pulse lengthening circuit I3, by which more of the pulse repetiton rate and its lower harmonics are introduced into the signal. The pulse lengthening circuit may consist of any well known circuit which effects an integration of the applied signal. The signal is then amplified in an audio amplifier I4 and is applied to a reproducer I5 in which the pulse repetition rate of the received signal is heard. The receiver circuit is tuned by adjusting the bar that extends transversely across the pair of parallel wires that form parts of the lecher line 3 and the detected signal is listened in upon at the reproducer I5 for maximum loudness of tone.

When the set is in operation as a receiver, signal that is received on the antenna I and that is coupled into the superregenerative oscillating part of the circuit, is rectified in the cathode plate circuit of the magnetron 4 due to the well-known detector action of a superregenerative oscillating circuit. When the set is receiving, a rectified voltage is formed across the resistance 5. 1i the received signal is of a longer duration than the period of the quench voltage that is supplied by the supersonic frequency from the oscillator I 0, the rectied voltage of the magnetron 4 will consist of unidirectional pulses at quench frequency. More commonly, however, the received signal is a pulse of a shorter duration than the period of the quench voltage. When the signal pulse is of short duration, a single amplified pulse is detected. If the received signal pulse occurs during the blanking part of the quench cycle, it is possible that no detection will occur, but in practice this is found not to be a serious impediment to operation.

For operation as a transmitter, the circuit is altered by throwing the switch 9 to its transmit position. The switch I8, being preferably ganged to the switch 9 as shown, is closed when the switch 9 is closed to the transmit position, thereby shorting out the resistor 5. The shorting out of the resistor 5 increases the plate Voltage of the magnetron 4 to a value that is suitable to induce the sustained oscillation of the magnetron 4 at substantially the same frequency as that to which it previously responded as a detector. shorting of the resistor 5 also removes signal from the video amplifier I2. When the switch 9 is in the transmit position the oscillator I is disconnected and the noise source I1 is applied to the grid of the modulator tube 8. The noise source I1 applies noise modulation through the modulator tube 8 to the radio frequency oscillation of the magnetron 4 from which, by induction, the transmitting radio energy, such as jamming noise or the like, is emitted from the antenna I.

The device is operated simply and rapidly by throwing the switches 9 and I8 to their receiving positions, tuning the receiver to the desired signal, and then throwing the switches 9 and I8 to their transmitting positions. The transmitted signal is in this manner tuned directly on the frequency of the intercepted signal and emits radio energy or, where desired, effectively jams the enemy signal that has been intercepted.

The modified circuit for the device that is contemplated herein and that is shown in fragmentary form in Fig. 2 of the accompanying drawing, comprises the substitution of the battery shown in Fig. 1 by an alternating current power suppli7 I9 that is fed thru a variable transformer 20 and a power rectifier '2l to the movable switch arm of the switch I8 and to the connector between the resistor and the condenser II. The transformer preferably is variably controlled from the switch 9, as shown.

The cited modification in circuit compensates for the fact that the frequency of a magnetron is responsive to changes in its plate voltage, such as when the switch I 8 is closed or the like. Normally this change in plate voltage does not materially impair the proper functioning of the circuit since the change in the plate voltage of the magnetron 4 between its superregenerative operation and the transmitting oscillation is approximately 100 volts in a total of 2000 volts.

In the transmitting position, the modulation that is introduced into the circuit of the magnetron 4 both amplitude and frequency modulates the magnetron 4 by the operative functioning of the magnetron. When transmitting, therefore, the magnetron 4 emits from the antenna I a band of frequencies which is suficiently broad so that it covers the frequency of the received signal even in the presence of some shift of the central frequency of the transmission.

In the modification that is shown in Fig. 2 of the drawings, such slight frequency shift as exists in the transmission is satisfactorily corrected. In this adaptation to an alternating current power supply in the plate current of the magnetron 4, the control of the variable transformer 20 is connected to the switch 9 so that when the switch 9 is thrown from its receiving position to its transmitting position the variable transformer 20 is varied in its transformer ratio sufficiently to correct for substantially any other frequency changing effects which may be operative and holds the frequency of the magnetron 4 substantially constant without requiring the retunng of the lecher line 3. In this manner the circuit modification that is shown in fragmentary form in Fig. 2 stabilizes the radio energy output of the set with a minimum of required attention.

Limited modifications in circuit arrangement and substitutions of components in the herein described illustrative circuit that result in satisfactorily functioning devices may be made Without departing from the scope of the present in- Vention.

What I claim is:

1. A repgiver-transmitterusystem including an electron tube having at leasta-plte and a cathode, an adjustable source of positive potential, a load resistor connected between said plate and said potential source, signal translating means connected across said load resistor, a cathode return circuit for connecting said cathode to said source of potential, switching means, a first circuit coupled to saidtube in a first position of saidfsjvi'ffitching-meaii's for"`causing said tube to function asa, `detector, a second circuit coupled to said tube in an'sfgglgndpositionof `said switching means lfor causing lsaid tube 'to function as a transmitter, means for shorting said load resistor in said second position and simultaneously decreasing the voltage of said source of potential so as to maintain the voltage on said plate in said second position equal to the Voltage on said plate in said first position, whereby the frequency of the system remains constant whether it is operating as a transmitter or receiver.

2. A device as defined in claim 1, wherein said tube functions asY anngwscillating detector and said first circuit includes means Vforwn'""c"'i'lftiig said tube with a quench voltage, thereby causing said tube to function as a superregenerativg detector when said switching means s`iin'sid first position.

3. A device as defined in claim 1, wherein said tube is a magnetron.

4. A device as defined in claim 1, wherein said second circuit includes means for modulating said tube with a noise voltage, thereby causing said tube to function was aujgmrrringjgnusmmitter when said switching means is in said seconcmibsition. r'

5. A combination receiver-jammer radio device, comprising in combination, means for intercepting signals, a lecher line having an adjustable shorting bar thereacross and being inductively coupled with said signal intercepting means, a magnetron tube inductively coupled to said signal intercepting means by said lecher line, a modulator tube having its space current path in series with the plate-cathode circuit of said magnetron tube, a,oscihatorwgeneratingna supersonic frequency, a noise` source for producing jamming signals, switching means for coupling said oscillator to the input circuit of said modulator tube in a first position thereof, whereby said device functions as a receiver, said switching,

means coupling said noise source to the input circuit of said modulator tube in a second posi- @ion thereof, a direct current source, a resistor interposed between the positive pole of said direct current source and the shorting bar of said lecher line, a pulse amplifier having its input circuit coupled to said resistor, means for shorting said resistor out of said pulse amplier input circuit when said switching means is in the second position thereof, whereby said device functions as a transmitter, a pulse lengthening circuit responsive to the output of Said amplifier for introducing lower harmonics into said intercepted signals, an audio amplifier responsive to the output of said pulse lengthening circuit, and means for reproducing the output of said audio amplifier.

EVERARD M. WILLIAMS.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Number Name Date 2,045,224 Gerhard June 23, 1936 2,106,770 Southworth Feb. 1, 1938 2,125,507 Ladner Aug. 2, 1938 2,130,381 Von Collas Sept. 20, 1938 2,415,317 Wheeler Feb. 4, 1947 2,416,794 Crosby Mar. 4, 1947 

